Firing circuit for voltage regulator tube



July 5, 1960 Q 5 BRAHM 2,944,206

FIRING CIRCUIT FOR VOLTAGE REGULATOR TUBE Filed March 23, 1955 INVENTOR.

CHARLES B. BRAHM LM 1M5 ATTORNEY FIRING emourr FOR VOLTAGE REGULATORTUBE United Aircraft Corporation, East Hartford, Conn,

5 a corporation of Delaware Filed ar. 23, 1195's, Ser. No. 496,108

4 Claims. c1. 323-16) This invention relatesto voltage regulatorcircuits and 'par't'icula rly to circuits" utilizing gaseous dischargetubes 7 including the firing-circuits for the tubes. Anfobject ofthisinvention is 'a'circuit for firing a gaseous discharge tube and alsolimiting the loss in the line."

A'further objectis 'a circuit utilizing the availableline Charlesuranium, Windsor Lo'cks, Conn, assignor to voltage for firing thetubeand limitingthe tube running" load to a --minimum.

A further object is a circuit utilizing a single. power source andseparate lines for firing the tube and for supplying the load so that;the power loss will be maintained at a minimum. I

Other objects and advantages will be apparent from the followingspecification and attached drawings: in

which:

Fig. l is a circuit diagram incorporating a voltage regulator includingthe'firing circuit of the invention.

Fig.'2 is a circuit diagram incorporating the invention utilizing theline voltage for firing the voltage regulator tube.

In voltage regulator tube circuits having a material voltage sourcevariation in which the minimum source voltage is above the firingvoltage, it becomes important to maintain the dropping resistancebetween the source and the voltage regulator tube at a maximum to keepthe total current through the dropping resistor at a minimum and onlyslightly above the load current. Normally where the linevoltage is usedto fire the tube the optimum dropping resistance cannot be used becausethe dropping resistance and the load resistance forms a voltage dividercircuit which will determine the voltage supply available at thejunction of the two resistors, where the volt age regulator tube isnormally connected. In order to obtain the necessary comparatively highvoltage supply to fire the tube, especially where the line voltage isonly slightly above the voltage necessary for firing, the droppingresistor must be made small in order to still have available at thejunction of the dropping and load resistors, where the voltage regulatortube is connected, a voltage supply high enough to fire the tube. Withsuch a small dropping resistor, the current through the droppingresistor and the tube becomes excessive when the tube starts to conduct,resulting in a high 1 R loss through the resistor or an overloading ofthe tube or both. If the resistance is made large enough to prevent thetube from overloading, it will then drop the line voltage so much thatat the minimumline voltage there will not be voltage supply enough leftat the junction of the dropping and load resistances to fire the tube.

lnorder to permit the use of an optimum dropping resistance in theoperating circuit, I have provided a separate circuit for firing thetube, thus allowing the dropping resistor to be the optimum resistancefor limiting the current through the voltage regulator tube to a minimumwhile providing sufiicient current to provide the necessary regulation.

In Fig. 1 the direct current source voltage is indicated lator tube.

is 2,944,206. Pa ent- 4 4 1 6! 2 p at E the dropping resistor R thevoltage regulator tube VR, the load resistant R and the load orregulated voltage supply E The voltage-regulator tube is connected at 10between the dropping resistance R and the load resistance R;, and arectifier CR is inserted in the line between the connection 10 and thevoltage regu- A second source of voltage Episconnected through adropping resistor R to the voltage regulator tube at point 12 so thatthe rectifier CR isolates this second source of voltage E from the loadresistance.

' Before the voltage regulator tube'starts to conduct, it

-acts as an open circuit to both 'the source voltage E 'and theauxiliary voltage E There will be-some-current flow through R and R fromthe source E5 which will make the voltage supply at 10 somewhat less"than the E voltage source. new will'be no current flow through R becausethe rectifier will block current flow through R and the voltageregulator tube is not conducting;

therefore, the full voltage of E will be applied across the rectifiertube to fire it and the resistance R, can be made high to limit thecurrent flow through the voltage i regulator tube'to the desired amount.R isjnot utilized in firingthe tube, it can' be made at the optimumvalue to supply the desiredrun'nin'g voltage As the resistance orvoltagesupply at po'i'nt- 10' with theoptimunr amount additional current overthe load current 'to'provide satisi factory operation of thevoltageregulator tube.

' The'voltage regulator tubehas'a range of currents at which it willsatisfactorily operate in regulating-"By utilizing the above system-inwhich a portion ofthe currentis' supplied from E through R 'and theremainder ';'"of the current is supplied fro'inE through R ,]it is sibleto design the resistors R and R so that an optimum current flow throughthe regulator'tubewill besufiicieiit to supply the necessary voltagedrop from the source E to the voltage supply point 10 to provide thedesired regulation even where the source E has a material variation,from from to volts. The rectifier CR will of course transmit currentfrom the source E through the regulator tube when the voltage regulatortube is conducting as both the rectifier CR and the regulator tube VRare connected to conduct in the same direction.

Where the voltage of the power source is equal to or above the firingvoltage, it is possible to use this source instead of an auxiliarysource for firing the tube and still have the resistance R an optimumresistance.

Fig. 2 shows the source voltage connected in a separate firing circuitto fire the voltage regulatortube with this second circuit incorporatingthe resistance R and isolated from the load resistance by the rectifierCR so that before the voltage regulator tube starts to conduct, the fullvoltage of the source may be applied as a voltage supply across thevoltage regulator tube to fire the tube and after the tube starts toconduct then the source E through the resistor R can supply theoperating circuit the voltage to be regulated with the resistor R chosento provide the minimum power loss while maintaining an efficientoperation of the voltage regulator tube. As before the resistance R, canbe chosen to provide a minimum power loss while assisting in theetficient operation of the voltage regulator tube. The rectifier CR, asbefore, will act to isolate the circuit including the resistance 3rectifier thus providing one circuit for firing the tube, which circuitcan be designed with an optimum resistance for low loss and efilcienttube operation and a second circuit for providing the voltage to beregulated with a dropping resistor which can also be designed for aminimum power loss with efiicient voltage regulation within theoperating limits of the tube current.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, and may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim:

1. In combination a direct current power source, a load connected acrosssaid source, a voltage regulator tube and a rectifier in seriesconnected across said source in parallelwith said load, means modifyingthe potential of said source in accordance with current flow throughsaid load and rectifier, a connection, including means modifying thepotential of said source in accordance with current fiow, connectingsaid source directly across said tube to provide a firing circuit forsaid tube.

I 2. In combination a source of direct current, two parallel connectionsfrom said source each having means dropping voltage in accordance withcurrent fiow through the respective connection, a voltage regulator tubeconnected directly across one said connection and connected in serieswith a rectifier conducting in the same direction as said tube acrossthe other connection.

, 3. In combination, a gas tube having a relatively stable forwardvoltage drop and a preferred range of variable current characteristics,a rectifier having a relatively low forward resistance and a relativelyhigh back resistance connected in series so that both the tube and therectifier have the same forward direction, a load connected across ,saidseries arranged tube and rectifier, an impedance voltage higher than thetube firing voltage to regulate the voltage applied to said load bycontrolling the voltage drop between said source and said tube and load,said impedance selected to provide the optimum operating conditions andthe preferred range of variable current in said tube, said impedancedropping the voltage of said source to below the firing voltage of saidtube due to the current flow through said load when said tube is notoperating, a relatively high impedance arranged in a firing circuitreceiving its entire voltage from said source and connected directlyacross said tube andsaid source in parallel with the circuit containingthe first mentioned impedance and isolated from said load by therectifier to supply a voltage from said mum to said tube unaffected bycurrent flow through the load to fire the tube.

4. In combination with a direct current operating circuit comprising, aseries arranged direct current voltage source, dropping resistor andload, a voltage regulator tube having a working voltage less than thedirect current voltage of said source and arectifier conducting in thesame direction connected in series across said load and voltage sourcesupplying all the voltage for said voltage pp y 7 References Cited inthe file of tLis patent UNITED STATES PATENTS Higgins Nov. 2, 1954 MedalOct. 16, 1956 OTHER REFERENCES Vacuum Tube Circuits, L. B. Arguimbau,John Wiley & Sons, 1948, p. 44.

